greg_in_canada
Flashlight Enthusiast
The U2 thread got me thinking about the two methods
of dimming. PWM is supposed to be better for tint
control but worse for efficiency (since the LED is
running at high current all the time with variable
amount of off time).
Assuming my understanding is correct perhaps a cross
between the two would be even better.
Suppose we have a Lux III running at full brightness
with 1000mA. For the first few steps of dimming we
stay at 100% duty cycle and just reduce the current.
Then for lower brightness levels the (peak) current
stays constant and the PWM duty cycle is reduced.
Say you could dim from 1000mA to 500mA to 250mA (constant
current) without too much tint change. Below that you
stay at 250mA current and reduce the duty cycle. So the
next dimming step would be 250mA 50%, then 250mA 25%
and so on.
The benefit would be the LED is run in its more efficient
current range (except at full brightness) but you
still get better tint at low brightnesses.
What do you think? Am I on base or off base with this?
Can anyone build such a circuit?
Cheers - Greg
of dimming. PWM is supposed to be better for tint
control but worse for efficiency (since the LED is
running at high current all the time with variable
amount of off time).
Assuming my understanding is correct perhaps a cross
between the two would be even better.
Suppose we have a Lux III running at full brightness
with 1000mA. For the first few steps of dimming we
stay at 100% duty cycle and just reduce the current.
Then for lower brightness levels the (peak) current
stays constant and the PWM duty cycle is reduced.
Say you could dim from 1000mA to 500mA to 250mA (constant
current) without too much tint change. Below that you
stay at 250mA current and reduce the duty cycle. So the
next dimming step would be 250mA 50%, then 250mA 25%
and so on.
The benefit would be the LED is run in its more efficient
current range (except at full brightness) but you
still get better tint at low brightnesses.
What do you think? Am I on base or off base with this?
Can anyone build such a circuit?
Cheers - Greg